In U.S. Pat. No. 2,641,607 (issued June 9, 1953), Albisetti et al describe the thermal reaction of a 2-alkenenitrile (e.g. acrylonitrile) with a neutral olefinic compound (e.g. isobutylene) in a first stage reaction to produce unsaturated mononitriles having a greater number of carbon atoms (e.g. 5-methyl-5-hexenenitrile). Albisetti et al state that the reaction effluent can be distilled to recover the unsaturated mononitrile product, and that the recovered unsaturated mononitrile product can be thermally reacted with a neutral olefinic compound in a second stage reaction to produce unsaturated dinitriles. The patentees state that the first stage reaction can be conducted in the presence or absence of an inert diluent or solvent. The patent lists hydrocarbons, ethers and esters as suitable inert organic solvents, and then states that the reaction also takes place in the presence of water as a diluent, the water serving as a heat transfer medium.
In J. Am. Chem. Soc. 78, pp 2637-2641 (1956), Albisetti et al describe further work with the thermal reaction of a 2-alkenenitrile with a neutral olefinic compound in a first stage and the subsequent reaction in a second stage of a neutral olefinic compound with the reaction product of the first stage to produce unsaturated dinitriles. The authors state that water can be employed as the reaction medium in the second stage reaction of acrylonitrile with 5-methyl-5-hexenenitrile to produce 5-methylenenonanedinitrile. The authors also state that in the case of polymerizable nitriles, the use of water as the medium prevented formation of tars.
In U.S. Pat. No. 3,840,583 (issued Oct. 8, 1974) Turk et al disclose that the yield of unsaturated dinitriles can be increased by contacting an unsaturated mononitrile, an olefin and a monoadduct reaction product of an unsaturated mononitrile and an olefin, wherein the monoadduct reaction product is present in significant amount during substantially the entire reaction period. The patentees stated that this single stage reaction could be carried out in the presence or absence of a solvent or diluent which is nonreactive with either the reactants or the reaction products. The patentees list various hydrocarbons, various ethers, tetrahydrofuran, dioxane, carbon tetrachloride and methylene chloride as representative commercially available nonreactive solvents that can be employed.
A significant improvement over the known processes has been described in U.S. Pat. No. 3,985,786. This patent describes the discovery that the utilization of an aqueous medium as the diluent in the Turk et al single stage process provides a greater increase in yield of unsaturated dinitriles than would be expected from the summation of the increase in yield of unsaturated dinitriles achieved by the utilization of water as the diluent in both stages of the Albisetti et al process and the increase in yield in unsaturated dinitriles achieved by the utilization of the Turk et al single stage reaction instead of the Albisseti et al two stage process.